Ultraviolet (UV) lamp systems may be either microwave power UV lamp systems or medium pressure mercury vapor “ARC” lamp systems. UV lamp systems are used in high speed manufacturing processes to cure inks, coatings, and adhesives in a variety of applications. These applications may include, for instance, decorating, laminating, hard-coat protection, circuit board conformal coatings, and printing. UV lamp systems are also used to manufacture silicon semi-conductor wafers. Additionally, UV lamp systems may also be used for exposing imaging printing plate templates.
The typical UV lamp system includes an irradiator to produce high intensity UV light, a power supply to provide electrical power to the irradiator, and an interconnecting high voltage cable. The microwave power UV lamp system has an irradiator that is equipped with one or more magnetrons. The magnetrons convert the electrical power received from the power supply to Radio Frequency (RF) energy at approximately 2450 MHz. The microwave energy produced by the magnetrons in the irradiator is guided into a cavity which is captivated by an RF screen. An electrodeless medium pressure mercury-vapor lamp (or bulb) is positioned inside of this cavity. For UV curing applications, the bulb is typically formed in the shape of a tube with a slight “hour-glass” shape, and is constructed of quartz. For imaging and semi-conductor applications the bulb is typically spherical. The bulb may be filled with mercury, argon, and/or metal halides such as iron and gallium. The fill inside of the bulbs may absorb the microwave (RF) energy and, consequently, change to a plasma state. The plasma produces radiation energy in the UV lamp system which is the form of UV, visible, and infrared energy.
The UV lamp system is provided with an RF screen in order to captivate and seal the RF energy within the cavity where the electrodeless bulb is positioned in the irradiator. A conventional RF screen 10 is shown in FIG. 1. The RF screen 10 is composed of a metal frame 18 with a fine mesh screen 12, usually made of tungsten, retained thereon. As can be seen in FIG. 2, a metallic wire-woven mesh gasket 14 may be employed in order to provide a seal between a main reflector and end reflectors of the UV lamp system, and between the main reflector of the UV lamp system and the metal frame 18 of the RF screen 10. The gasket 14 is compressed between the metal frame 18 and a reflector when the RF screen 10 is attached.
The RF screen 10 prevents RF energy from escaping into the surrounding environment, and subsequently allows the bulb of the UV lamp system to light. A defective RF screen 10, such as one with a hole or other defect, would allow RF energy to escape and prevent the bulb of the UV lamp system from lighting, or cause a reduced output in the bulb of the UV lamp system. Additionally, an improperly installed RF screen 10 will cause arcing, and thus damage to components inside of the irradiator. Further, an RF screen 10 with deformed or worn gaskets 14 will also cause arcing and damage to the irradiator.
The RF screen 10 is attached to a reflector which helps define the cavity in the UV lamp system. FIG. 3 shows a conventional reflector 32 used in current UV lamp systems. The reflector 32 is provided with a plurality of holes 68 through which screws may be inserted so as to connect the RF screen 10 to the reflector 32. Referring to FIGS. 1 and 2, the screws may be disposed through holes 16. The use of screws is problematic in that they may be lost when the RF screen 10 is removed. If lost, the screws may not be replaced by the user of the UV lamp system, resulting in improper and non-uniform pressure on the metallic wire-woven mesh gasket 14. This in turn could cause arcing between the RF screen 10 and the reflector, resulting in damage to components of the UV lamp system such as the RF screen 10, reflector, magnetrons, metallic wire-woven mesh gasket 14, and the bulb. Arcing may also reduce the coupling efficiency of the RF energy to the bulb, thus reducing the bulb's output.
Additionally, screws may be stripped during removal or insertion, resulting in improper torque on the screws, and thus improper tightening of the RF screen 10. This in turn may create gaps between the reflector and the metal frame 18 of the RF screen 10, causing arcing in certain areas. Screw threads may also be stripped when inserting the screw at an improper angle. This may cause damage to the female threads in the reflector to which the RF screen 10 is attached, possibly resulting in a need to replace the entire reflector assembly. Over-torqueing of the screws may create too much pressure causing a permanent deformation of the metallic wire-woven mesh gasket 14 and will in turn cause gaps if the RF screen 10 is removed and replaced without the same amount of torque on the screws. If the screws are not properly tightened, gaps or insufficient surface contact with the metallic wire-woven mesh gasket 14 may result to also cause arcing.
UV lamp systems that employ screws to attach the RF screen 10 require the removal of 4 screws for a 6-inch irradiator, and 8 screws for a 10-inch irradiator. Removing and replacing these screws during removal/replacement of the RF screen 10 is a very tedious and time-consuming process, especially when the UV lamp system employs many irradiators. This results in increased maintenance time, and leads to more machine downtime for the UV lamp system.
The present invention improves upon current UV lamp systems by providing for an improved attachment of the RF screen 10. As a result, the amount of damage to the UV lamp system is reduced, the efficiency of the UV lamp system is improved, and the amount of downtime to the UV lamp system is reduced.